Solubilization of steroid hormones by polyoxyethylene lauryl ether.

As a further approach to an understanding of a relationship between the magnitudes of micellar solubilization and the hydrophobicities of solubilizates, steroid hormones (19 species) were selected to explore the meaning of the intercept b value. Two linear free energy relationships were established between the aqueous-polyoxyethylene lauryl ether micellar partition coefficient (K) and the partition coefficient (Poctanol) between aqueous solution and n-octanol. One consisted of the steroids carrying a fluorine atom at a carbon 9 and the other of those carrying no fluorine atom. The b value predicted that the fluorine steroids are solubilized in the outer layer of the mantle while the others are incorporated into rather inner position, which was consistent with the experimental results.